1. Field of the Invention
This invention relates in general to a signal processing system for a group III facsimile, and more particularly concerns a signal processing system in which the portions of a document to be transmitted are identified in accordance with whether or not they are to be transmitted, in order to transmit selectively the document information.
2. Description of the Prior Art
In the field of facsimile systems in which document information is converted to electrical signals by document scanning and the signals are transmitted in the form of scanned output signal waveforms without eliminating the redundancy of the document information, there is known a system which reduces the transmission time by applying special marks to portions of a document to be transmitted to transmit the scanned output signals which correspond to only the marked portions, for example, as shown in Japanese Patent Application Kokoku (Post-Exam. Publn) No. 11451/72, entitled "Facsimile". However, in such a system, the sub-scanning rate is switched according to the absence or presence of the marks, and in order to reduce the transmission time, the send side facsimile must send that switching information to the receive side facsimile which, in turn, performs a special operation only when receiving the information. Therefore, the above-mentioned system always requires a combination of special send and receive facsimiles each with the above-mentioned additional function.
This means that the system has no compatibility with existing facsimiles.
In addition, in such a conventional system, there has been a defect in that the system cannot be applied to a facsimile of the type which encodes scanning signals and after eliminating the redundancy of the document information, transmits them, for example, to a group III facsimile which operates according to run length code signals or code signals which correspond to the two-dimensional correlation of document.